Various chemical compounds, commonly referred to as dopants, are utilized in semi-conductor device fabrication. In general, the liquid dopant source material is stored in a bubbler container having gas inlet and outlet fittings at its top, and a carrier gas is passed through the inlet and bubbles through the liquid dopant in the bubbler container before passage into the bubbler outlet. The vapor pressure of the liquid dopant varies with temperature and it is necessary to maintain the liquid dopant in the bubbler container at a substantially constant preset temperature to control dopant level in the semi-conductor processing furnace.
In a typical installation, the source bubblers are placed on shelves in a gas cabinet at one end of the furnace tubes of the semi-conductor processing furnace. The furnace tubes are heated to a very high temperature, commonly of the order of 1000.degree. C., and the radiant heat from the furnace tubes raises the temperature in the gas cabinet and aggravates the problem of maintaining the liquid dopant source material at a preset temperature. Further, the shelves in the gas cabinet are commonly spaced apart a distance of the order of about twelve inches and this limits the permissible overall height of the temperature controller with the bubbler container installed.
Top loading type thermo-electric temperature controllers for bubbler containers have heretofore been made having an open top well for receiving the bubbler container and which well was heated or cooled by thermo-electric devices to control the temperature of the contents of the bubbler container. The container receiving wells included a container support platform of thermally conductive material disposed in heat exchange relation with thermo-electric devices to be cooled or heated thereby, and a sleeve of thermally conductive material that extended upwardly from the platform around the bubbler container to enhance heat transfer to and from the bubbler container and also shield the sides of the bubbler container from the temperature of the surrounding atmosphere. However, such top loading thermo-electric temperature controllers require a very high overhead clearance above the top of the temperature controller in order to enable installation and removal of the bubbler container from the well, and this limited their usefulness in applications where the clearance over the top of the temperature controller is limited.
Thermo-electric controllers for bubbler containers have also heretofore been made, as disclosed in U.S. Pat. No. 4,487,619, in which the housing was formed with a side opening door to allow installation and removal of the bubbler container from the side of the temperature controller. Since the bubbler containers can be loaded and unloaded from the side of the temperature controller, such temperature controllers require only a small overhead clearance sufficient to accommodate the fittings and tubes for the bubbler container. However, such prior side loading thermo-electric temperature controllers cooled or heated the bubbler container only through contact with the bottom of the bubbler container and relied upon thermal insulation material on the inner sides of the housing and door to reduce heat transfer between the bubbler container and the surrounding atmosphere.